Heat transfer supply for vacuum metalizer

ABSTRACT

AN IMPROVED MEANS FOR SUPPLYING HEAT TRANSFER FLUID AND TORQUIE TO A DRUM IN A VACUUM CHAMBER THROUGH THE USE OF A DRIVE SHAFT SEPARATE FROM AN AXIAL FLUID SUPPLY SHAFT.

United States. Patent Edward De Buhr Chadds Ford, Pa.

Feb. 13, 1969 June 28, 1971 E. I. do Pout de Nemours and Company Wilmington, Del.

Inventor Appl. No. Filed Patented Assignee HEAT TRANSFER SUPPLY FOR VACUUM METALIZER 3 Chims,2 Drawing Figs.

05. Cl. 165/89, 1 18/48 Int. Cl. F28f 5/02 Field of Search 118/48, 49.5, 50, 50.1, 117 (lnquired); 165/86-92; 165/89 [56] References Cited UNITED STATES PATENTS 2,015,747 10/1935 Drake 165/90 3,082,124 3/1963 French et a1... 1l8/49X 3,484,853 12/1969 Mishi 285/134X FOREIGN PATENTS 926,069 5/ 1963 Great Britain 1 18/49 Primary Examiner-Meyer Perlin Assistant Examiner-Theophil W. Streule Attorney-Donald W. Huntley ABSTRACT: An improved means for supplying heat transfer fluid and torque to a drum in a vacuum chamber through the use of a drive shaft separate from an axial fluid supply shaft.

PATENTEU JUH28 I971 llllllIJi INVENTOR EDWARD De BUHR HEAT TRANSFER SUPPLY FOR VACUUM METALIZER BACKGROUND OF THE INVENTION In high temperature vacuum treatment of organic film, such as the deposition of a vaporized metal, the organic substrate is generally moved on a rotating support drum. It is essential to remove the heat from the support to prevent overheating and distorting the organic substrate. It is the practice, therefore, to cool the support by circulating a cooling fluid through the interior.

One basic problem of circulating fluids to elements in a vacuum environment, especially those involving rotating elements, is the prevention of the escape of volatile liquids into the vacuum. Such escape would not only put an additional load on the vacuum pumping system, but, in vacuum metallizing, would also interfere with the free and uncontaminated flow of vapor from its source to the substrate. Water, by virtue of its low viscosity and high heat capacity, is one of the most desirable fluids for a cooling system using a circulating fluid. Its volatility and the large volume of gas generated upon its vaporization, however, have required particularly high standards of performance for the equipment and seals associated with supplying the water to the rotating drum. Among the many equipment setups which were devised to solve this problem, one of the more satisfactory is one in which the fluid is transferred to the shaft of the drum support in the vacuum enclosure, the fluid being fed through a rotary seal which employs a tightly rubbing graphite surface. This particular method requires frequent maintenance, however, since even a minor failure can cause a catastrophic loss of vacuum causing severe damage to the pumping system.

Another mechanical expedient employed is to supply the fluid to the drive shaft of the rotating support member outside of the vacuum chamber. This approach involves the supply of the fluid and its return through a shaft of sufficient rigidity to convey torque for rotation. Difficulty arises from several essential features of this arrangement. It is necessary to support the rotating drum by bearings at each end, and have a third bearing at the wall of the enclosure to seal the vacuum environment from the external atmosphere. The three-bearing arrangement, coupled with the necessarily rigid shaft for torque transmission, makes alignment difficult. Alignment is very critical for coating continuous webs, especially with a metal subdivided into separate lanes on metallized film for capacitor use. Further, poor alignment results in excessive wear of the bearing seal, permitting leakage of air into the vacuum enclosure.

Still other attempts to circumvent the problem involved the substitution of less volatile and more viscous cooling fluids to reduce the degree of sophistication necessary for apparatus to convey the fluid in or out of the drum through the drive shaft. However, the corresponding loss of heat transfer capacity made this an unacceptable alternative.

SUMMARY OF THE INVENTION The instant invention provides an apparatus which simplifies the supply of coolant and torque to the support drum, permits more exact alignment of the elements, reduces wear on the elements and permits the safe use of water as the cooling fluid.

Specifically, the invention relates to an apparatus for the treatment of thermoplastic film in a vacuum chamber wherein the film is supported on a cooled rotatable drum in the chamber, and an improved means for supplying torque and cooling fluid to the drum from outside of the chamber which comprises a first shaft having two concentric channels formed therein for the supply and return of fluid to and from the drum, the first shaft positioned axially to the drum,journaled within a hermetic bearing in the chamber wall, and joined to the drum with a flexible, hermetic, coupling; a source of torque outside of the chamber mechanically coupled to a second shaft journaled in a hermetic bearing in the chamber wall; and means inside the chamber for mechanically coupling the second shaft to the drum to cause the drum to rotate.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side view of a vacuum metallizer incorporating the present invention, with ,the outer wall of the vacuum chamber cutaway.

FIG. 2 is a partially sectional enlarged view of a portion of FIG. 1 showing basic elements of the present invention.

7 DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention will be more clearly understood by reference to the drawings, which illustrate one particular embodiment of the invention. FIG. 1 schematically illustrates a vacuum metallizer utilizing the present invention for circulating a heat transfer fluid to the quench drum, with a separatequench drum drive shaft through the wall of the vacuum chamber. Support wall 10 upon which the interior operating elements of the metallizing apparatus are supported, is in the vertical plane perpendicular to the paper, and forms a vacuum-tight seal from the atmosphere at ring 11 with removable enclosure 12. Evacuation port 13 is coupled to a source of high vacuum, not shown, for maintaining a vacuum environment in the enclosure at the very low pressure required, for metal vapor deposition. Substrate 14, supplied from roll 15, partially wraps and is in contact with rotating quench roll 16, which moves it adjacent vapor source 17; optional mask 18 is often interposed between source 17 and substrate 14 when metallizing film destined for electrical capacitors to provide unmetallized lanes on the coated substrate. Coolant, preferably water, is supplied to mask 18 by supply pipe 19 and return pipe 20.

The particular features of the present invention are in the method of supplying a heat transfer fluid and driving power to the substrate quench drum 16. In order to maintain the precise alignment of quench drum 16 required for precisely located unmetallized lanes on the substrate, and to reduce the load on sea] bearing 22 in support wall 10, it is desirable to have bearings to support the shaft of quench roll 16 shown here as inboard bearing 23 and outboard bearing 24. In the present in-' vention coolant is supplied and returned through hollow shaft 25 which has a central channel to convey coolant to the quench drum and a concentric outer channel for return of the coolant. Drive power for rotation of the quench drum is supplied by motor 26 coupled by means of shaft 27 to chain drive 28 which supplies torque to rotate drum 16.

One of the principal benefits of the present invention is derived from-the capability of employing separate flexible couplings for the heat transfer fluid supply which communicates through the wall, and the power supply which separately communicates through the wall to supply torque.

These flexible couplings reduce wear on the airtight bearings through the enclosure wall to maintain a seal between the highly evacuated interior of the enclosure and atmospheric pressure on the exterior. The other functions of each of the flexible couplings, one transmitting a fluid without leakage to the vacuum environment and the other transmitting torque without mechanical loss of backlash to drive the roll, are not completely compatible in long term use.

These elements are illustrated in greater detail in FIG. 2. The numerals common to both drawings indicate the same elements. Shaft 25, as indicated hereinbefore, is made up of concentric tubes, having an outer channel 29 and inner channel 30, which respectively supplies fluid to and drains it from quench drum 16. Inner tube 31 separates the inner and outer channels; it may be a semirigid rubber tube, with appropriate couplings at its supply and drum ends. Rubber hose connection 32 couples hollow shaft 25 to nipple 33 on the axis of drum l6, and is held in place by hose clamps 34. Mechanical flexible coupling 35 provides flexibility to power shaft 25 between chain drive 28 and motor 26, not shown in FIG. 2.

Communication of fluid-conveying coolant shaft 25 and power shaft 27 through wall 10 is by means of rotary motion fed through conventional hermetic bearings 22 and 36. Fluid can be removed and supplied to the coaxial tubes of shaft 25 by means of ball bearing rotary union 38 which has a self-contained rotary siphon.

ln vacuum metallizing of film for capacitors employment of apparatus of the present invention, with separate shafts for coolant and torque, with rotary fluid transfer elements outside the vacuum enclosure enables longer periods of operation free of bearing maintenance and with reduced leakage of fluid into the chamber than with fluid transfer means within the drum, or with a common shaft for fluid and torque.,By eliminating the driving function of the axial fluid supply shaft, a flexible joint can be used, making alignment of the apparatus easier.

While the description provided has been directed primarily to supplying a heat transfer fluid to cool the backup drum during condensation of a metal vapor, those skilled in the art will readily appreciate the applicability of the instant invention to driven drums having other functions which require heating or cooling in combination with driving torque, and which require precise alignment, such as a heat roll for film conditioning. Such rolls may precede the deposition and may be driven at a speed slightly higher than the film supply speed to apply a slight draw to the film for wrinkle removal.

I claim:

1. In an apparatus for the treatment of thermoplastic film in a vacuum chamber wherein the film is supported on a cooled rotatable drum in the chamber, an improved means for supplying torque and cooling fluid to the drum from outside of the chamber which comprises a first shaft having two concentric channels formed therein for the supply and return of fluid to and from the drum, the first shaft positioned axially to the drum, journaled within a hermetic bearing in the chamber wall, and joined to the drum with a flexible, hermetic, coupling; a source of torque outside of the chamber mechanically coupled to a second shaft joumaled in a hermetic bearing in the chamber wall; and means inside the chamber for mechanically coupling the second shaft to the drum to cause the drum to rotate.

2. An apparatus of claim 1 wherein the means for coupling second shaft to the drum comprises a chain drive.

3. An apparatus of claim 1 wherein the first shaft is connected to a ball bearing rotary union exterior to the vacuum chamber providing a source and outlet for the heat exchange fluid. 

